Generator sets typically employ an internal combustion engine, such as a diesel engine, and a generator, such as a radial gap generator. These generator sets are employed in a multitude of differing environments for generating electrical power. Where a typical radial gap generator is employed, the generator set will have a substantial axial length. For example, in many cases, the rotor shaft of the generator is directly coupled to the main shaft of the engine. The axial length of the set then is the total of the length of the engine plus the length of the generator. Because radial gap generators are typically relatively elongated in the direction parallel to the axis of rotation, it is necessary that the generator rotor be mounted in bearings at one or both ends of the rotor which further increases the axial length of the generator, and thus the length of the generator set.
To adapt such sets to environments where long axial lengths cannot be tolerated, attempts have been made to offset the axis of rotation of the generator from the axis of rotation of the engine and couple the two via gears or belts. While such constructions avoid the problem of excessive axial length, reliability and/or weight problems are introduced by reason of the need for belts and/or gears to transmit power from the engine to the generator. Maintenance requirements in such systems are also increased as a result.
One typical usage of a generator set where axial compactness, high reliability and low maintenance are desired is in a mobile refrigeration unit. For example, such generator sets are often used in refrigerated trailers to provide electrical power to drive a compressor for a vapor compression refrigeration system. Not infrequently, the system components are relatively inaccessible, making it highly desirable that the system be extremely reliable with low maintenance requirements.
The present invention is directed to overcoming the above problems by providing an axially compact generator set where the generator may be directly coupled to an internal combustion engine and which is ideally suited for, but not limited to, use as a source of electrical power for a mobile refrigeration unit.